1. Technical Field
The present invention relates to rotary rock cutters. In particular, it relates to an earth-boring rock cutter mount and cutter assembly for use in conjunction with a raised bore head-plate for widening the diameter of a bore hole.
2. Background Art
Industrial earth-boring cutter assemblies, such as the type used in conjunction with a raised bore head-plates for widening the diameter or a bore hole are well known in the art. These assemblies have evolved along a common conception in the design of rotary cutters. Up until now, a few such examples exist. As shown in FIG. 1, one such example is shown and described in U.S. Pub. No. 2002/0166702 (filed May 7, 2002) to Cariveau et. al. As described therein, this conception in design generally includes cutter 1, an a central journal assembly 2 on which a cutter body 3 is rotatably mounted. The cutter body 3 generally includes ribs and hardened inserts 4 to break up and crush the outer diameter surface of a bore hole when the cutter body 3 is pressed against and rolled over the formation 5. The cutter 1 is a raised bore cutter, which includes a ball bearing 10 and roller bearings 11 disposed between the journal assembly 2 and the cutter body 3 to allow the cutter body 3 to rotate freely with respect to the journal assembly 2. The ball bearing 10 is usually provided to carry an axial load through the bearing, and the one or more roller bearing 11 are typically provided to carry radial loads. In this configuration, the roller bearing 11 are placed around the journal assembly 2 prior to sliding the journal assembly 2 into the cutter body 3. Then the ball bearing 10 is put into place by inserting bearing balls through the ball hole 13 in the journal 2. Once the bearing balls are in place, a ball plug 12 is inserted into the ball loading hole 13 and then a ball plug retainer 14 is inserted into the journal 2 to retain the ball plug 12 in place.
To alleviate concerns relating to damage caused to the bearing balls of the ball bearing 10 and edges of the ball loading hole 13, cutter designs, known in the art, have the ball hole 13 placed at, or near, 180 degrees from the load bearing zone of the journal assembly 2. While this configuration ensures little or no load on the ball loading hole, this design does not allow for rotation of the journal in order to prolong journal bearing surface life.
Another example is also shown and described as the subject matter in U.S. Pub. No. 2002/0166702 (filed May 7, 2002) to Cariveau et. al. There, Cariveau et al. discloses a rotatable journal for an earth-boring cutter which includes a bearing journal adapted to be coupled to a cutter body. The first mounting end of the bearing journal is shaped to enable rotationally fixed position in a corresponding yoke. The yoke is operatively coupled to the body of the cutter. A single ball race is formed in an exterior surface of the journal. The loading passage is formed in the journal. The ball loading passage has an exit hole on the race. The hole is positioned so that is disposed in a rotary orientation which is at a selected angular displacement from the maximum radial loading of the journal. The first mounting end and the corresponding yoke are adapted to enable a plurality of rotary orientations. Each of the rotary orientations is such that the hole is oriented other than in the direction of maximum radial loading. As described therein, Cariveau et al. seeks to increase bearing life as a result of spalling and flaking off of material from the journal bearing surface by permitting rotation of the journal so that a previously unloaded surface may be subsequently used to carry load while maintaining the ball loading in an angular orientation outside of the load bearing zone.
While the foregoing examples offer some utility, a major disadvantage in each lies in the fact that, while they do provide for some alleviation of damage to the bearing balls, the journal surface, and ball loading holes by locating the ball loading hole in a position outside of the load bearing zone and for rotation of the journal, they are complex in design, are thereby costly in manufacture and service. Thus, it is desirable to provide a ball bearing earth-boring mount and assembly which is capable of rotation, simple in design, and less costly in manufacture and servicing. It is also desirable to provide an earth-boring cutter which eliminates the concerns, of the prior art, relating to the orientation of the ball loading exit hole in relation to the load bearing zone, but which also satisfies a need to prolong bearing and journal life. The present invention satisfies these needs.